In production processes of electronic parts such as IC's, for example, semiconductor wafers of a large diameter are diced, cleaned, dried and expanded while adhered to an adhesive sheet, then picked up and mounted. Adhesive compositions used for such adhesive sheets must have sufficient adherence to chips from the dicing step to the drying step, while being easily stripped from chips during pick up.
While Patent Document 1 discloses an energy ray curable pressure-sensitive adhesive composition that can be used for the above-mentioned purpose, further development of adhesive compositions with even better chip-holding properties during dicing and from which chips can be more easily separated during pick up has been desired.
On the other hand, Patent Document 2 proposes an adhesive composition in which two kinds of (meth)acrylic acid ester copolymers of different weight average molecular weights are used. The adhesive composition described in the document has excellent adhesion properties to the adhered object and bond durability, and is capable of following the expansion and contraction of substrates even under conditions of high temperatures and high humidity, but it does not satisfy the ease of stripping required of adhesive compositions used in the above-mentioned production processes of electronic parts.    Patent Document 1: Japanese Patent No. 2984549    Patent Document 2: JP-A 2001-89731